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Table 3 Power calculations for the Counselling for Alcohol Problems trial

From: The effectiveness and cost-effectiveness of lay counsellor-delivered psychological treatments for harmful and dependent drinking and moderate to severe depression in primary care in India: PREMIUM study protocol for randomized controlled trials

Outcome

Total sample size

Number per arm

Number of clinics

Treatment arm

Enhanced usual care arm

Effect size

Power

Mean standard ethanol content consumed in past two weeks

400

200

8

  

0.4a

82%

 

400

200

8

  

0.45

93%

 

400

200

8

  

0.5

97%

AUDIT score < 8 at 12 months

400

200

8

60%

40%b

-

84%

 

400

200

8

68%

40%b

-

99%

  1. aBased on the effect size in the meta-analysis by Vasilaki et al. which found an effect size of 0.4 (95% CI: 0.36, 0.44) for Motivational Interviewing versus no treatment in reducing alcohol consumption among non-dependent drinkers [41]. bBased on the randomized controlled trial by Bager et al., which found abstinence rates of 68% versus 40% two months after randomisation [42].